In Morocco, a small trickling filter was installed to receive pre-treated wastewater. The filter had a volume of 9.5 m³ (3 m high, 2 m diameter). It was built using bricks, stainless steel pipes and plastic net. For filter media, pipes commonly used for electric cable installations were cut into small pieces (ca 5 cm in length). A specific surface area of 250 m²/m³ was calculated.

On the surface of the filter, the up-flow wastewater sprinkler system based on perforated stainless-steel tubes was installed.

Holes (4 – 5 mm diameter) were added to the pipes (every 30 cm).

A test was carried out to determine the impact of the hydraulic loading rate on the removal efficiency for BOD and COD. The results are presented in the following table:

	Test 1 with HLR = 24 m³/d		Test 2 with HLR = 84 m³/d
	Inflow	Outflow	Inflow	Outflow
BOD (mg/L)	183	19	180	35
COD (mg/L)	500	58	511	118

Treatment Performance

The results show that the treatment performance is slightly higher at lower hydraulic loading rates:

Test 1 (low HLR): 88% BOD removal and 90% COD removal
Test 2 (high HLR): 81% BOD removal and 77% COD removal

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